Conventionally, a collision of a walker, a pedestrian or the like with a vehicle is detected by a device that is disclosed, for example, in Japanese patent document JP-A-2006-117157 (Also published as US patent document 20060087417). This obstacle detection device for vehicular use in the above disclosure includes an absorber, a pressure sensor, a speed sensor, and an airbag ECU device. The absorber absorbs an impact of the collision that is caused by a collision of an object on the vehicle. The absorber includes a chamber member and a connection member. The chamber member is connected by using the connection member, and is fixed on a front face of a bumper reinforcement. The inside of the chamber member, that is, a chamber, is filled with air. The pressure sensor is a sensor for detecting a pressure in the chamber. The pressure sensor is connected to the connection member through a tube. The speed sensor is disposed in a vehicle. The pressure sensor and the speed sensor are connected to the airbag ECU. The airbag ECU determines whether the colliding object that collides with the bumper of the vehicle is a walker based on a detection result of the pressure sensor and the speed sensor. More practically, whether the pressure inside the chamber exceeds a threshold that is determined based on the vehicle speed is used as a criterion for determination that the colliding object is a walker.
The obstacle detection device for use in a vehicle described above has the pressure sensor connected to the chamber member through a tube. Therefore, the chamber member proximity of the bumper reinforcement where the chamber member is fixed must have a pressure sensor arrangement space for installing the pressure sensor. For avoiding a preparation of the pressure sensor arrangement space, the pressure sensor may be connected on a back side of the chamber member. However, in that case, the pressure sensor has to be buried in a cut or the like in the bumper reinforcement for avoiding the interference with the pressure sensor. In either case, the pressure sensor makes it difficult for the obstacle detection device to be installed on a vehicle.